EP3404482A1 - Device for protecting an optical sensor and associated driving-assistance system - Google Patents

Abstract

The invention relates to a protection device (3) for an optical sensor (13) for a motor vehicle, said optical sensor (13) comprising an optic (14).

According to the invention, the protection device (3) comprises an optical element (9) configured to be arranged upstream of the optics (14) of the optical sensor (13) and having at least one surface (9a, 9b) of general aspheric form.

The invention also relates to a corresponding driving assistance system.

Description

The present invention relates to the field of driving assistance and especially to driver assistance systems, installed on certain vehicles, the driving assistance system may include an optical sensor, such as a camera comprising an objective, in particular comprising at least one lens. More particularly, the invention relates to a device for protecting such an optical sensor.

Currently, front, rear or side vision cameras equip a large number of motor vehicles. They are notably part of driver assistance systems, such as parking assistance systems, or line crossing detection systems.

Cameras are known that are installed inside the cabin of a vehicle against the rear window / window looking towards the rear from the rear window of the vehicle. These cameras are well protected from external climatic hazards and dirt caused by organic pollutants or minerals. However, the angle of view for such cameras, installed inside the cabin, is not optimal, especially for a parking aid, because they do not allow to see the obstacles in the vicinity of the rear of the vehicle for example.

For this reason, it is therefore preferred to install the cameras of the driver assistance systems outside the vehicles in different places according to the desired use, for example at the rear or front bumper, or at the level of the vehicle. rear registration plate or front of the vehicle. In this case, the camera is highly exposed to the projections of mineral or organic dirt that can be deposited on its optics and thus reduce its effectiveness, or even make it inoperative. Especially in rainy weather, there are projections of rain and dirt that can greatly affect the operability of the driver assistance system comprising such a camera. The surfaces of the optics of the cameras must be cleaned to ensure that they are in good working order.

To counteract the deposition of dirt on the camera, it is known to arrange a device for cleaning the optics of the camera, usually a nozzle of cleaning fluid, close to it, to remove the polluting elements that are filed during time. However, the use of these nozzles leads to an increase in operating costs of such a driving assistance system because they require the use of quantities of cleaning liquid quite important.

According to a known solution, means for vibrating a protective window of the camera are provided in order to remove the dirt from the protective window of the camera. However, it has been found that the effectiveness of such a device for stubborn and encrusted dirt can be limited despite the vibration of the protective glass.

According to another solution, the camera is arranged in a protective device. However, such a protective device is very bulky to install.

In addition, the use of such a protective device does not always make it possible to have a large viewing angle.

The present invention proposes to remedy at least partially the disadvantages mentioned above by presenting an alternative of a protective device of an optical sensor for preventing the deposition of dirt on the optical sensor such as a camera while maintaining a large viewing angle.

To this end, the subject of the invention is a device for protecting an optical sensor for a motor vehicle, said optical sensor comprising an optical element, characterized in that the protection device comprises an optical element configured to be disposed upstream of the optical sensor. optical optical sensor and having at least one surface of generally aspherical shape.

The one or more aspherical shapes make it possible to obtain a compact protection device without unduly deflecting the rays, and thus without greatly affecting the optical performance of the optical sensor that would be placed behind such an optical element.

It is understood that the one or more aspherical shapes are defined for each surface with respect to its overall profile, independently of the surface state and the roughness of this surface. For example, if one or more beads are made on the surface of the optical element to obtain an optical effect, for example diffusing, or to avoid stagnation of liquid surface, these beads are not considered as a participant in defining the general shape of the optical element and therefore are not considered to evaluate the aspheric nature of it.

• l'élément optique est au moins partiellement transparent ;
• ladite au moins une surface est une surface hyperbolique ;
• la flèche de ladite au moins une surface de l'élément optique en fonction de la distance radiale à l'axe optique de l'élément optique est donnée par l'équation (a) : $$z=\frac{{\mathit{<figure-callout\; id="2"\; label="cr"\; filenames="imgf0001.png"\; state="\{\{state\}\}">cr</figure-callout>}}^2}{1+\sqrt{1-\left(1+k\right)c^2{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="imgf0001.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}}+{\alpha }_1{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="imgf0001.png"\; state="\{\{state\}\}">r</figure-callout>}}^2+{\alpha }_2{\mathrm{<figure-callout\; id="4"\; label="r"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">r</figure-callout>}}^4+{\alpha }_3{\mathrm{<figure-callout\; id="6"\; label="r"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">r</figure-callout>}}^6+{\alpha }_4{r}^8$$
  
  dans laquelle :
  • c correspond à la courbure de la surface de l'élément optique,
  • r à la distance radiale à l'axe optique,
  • k à la constante conique, et
  • α_i[1,..,4] aux coefficients asphériques.
• la constante conique est inférieure à -1, de préférence inférieure à -50 ;
• la constante conique est comprise entre -50 et -200 ;
• la courbure de ladite au moins une surface de l'élément optique est comprise entre $\frac{1}{15}$
  
  mm^-1 et $\frac{1}{5}$
  
  mm^-1 ;
• l'élément optique présente une surface interne et une surface externe opposées, telles que la surface interne et la surface externe sont de formes générales asphériques différentes ;
• la surface interne et la surface externe vérifient l'équation (a) ;
• la constante conique est différente entre les équations (a) de la flèche de la surface interne et de la surface externe de l'élément optique ;
• les coefficients asphériques sont différents entre les équations (a) de la flèche de la surface interne et de la surface externe de l'élément optique ;
• l'élément optique est configuré pour être agencé à une distance inférieure à 5mm de l'optique du capteur optique, de préférence inférieure à 3mm de l'optique du capteur optique ;
• l'élément optique est configuré pour être disposé en amont de l'optique du capteur optique de sorte que l'axe optique de l'élément optique soit confondu avec l'axe optique du capteur optique ;
• l'élément optique est monté mobile en rotation autour d'un axe de rotation ;
• l'élément optique est disposé de façon centrée par rapport à son axe de rotation ;
• l'élément optique est agencé en amont du dispositif de protection de façon à faire face à une scène de route dont le capteur optique est configuré pour participer à la prise de vues ;
• ledit dispositif comporte un boitier solidarisé avec l'élément optique et présentant un logement configuré pour recevoir le capteur optique ;
• la surface interne présente une propriété antibuée, en particulier la surface interne dudit élément optique présente un revêtement antibuée ;
• la surface interne et/ou la surface externe présente au moins une propriété choisie dans la liste suivante : filtre infra-rouge, photocatalytique, hydrophobe, super hydrophobe, lipophobe, hydrophile, super hydrophile, résistance aux gravillons.

Said optical sensor protection device may further comprise one or more of the following features, taken separately or in combination:

• the optical element is at least partially transparent;
• said at least one surface is a hyperbolic surface;
• the arrow of said at least one surface of the optical element as a function of the radial distance to the optical axis of the optical element is given by equation (a): $$z=\frac{{\mathit{<figure-callout\; id="2"\; label="cr"\; filenames="imgf0001.png"\; state="\{\{state\}\}">cr</figure-callout>}}^2}{1+\sqrt{1-\left(1+k\right){\mathrm{vs}}^2{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="imgf0001.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}}+{\alpha }_1{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="imgf0001.png"\; state="\{\{state\}\}">r</figure-callout>}}^2+{\alpha }_2{\mathrm{<figure-callout\; id="4"\; label="r"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">r</figure-callout>}}^4+{\alpha }_3{\mathrm{<figure-callout\; id="6"\; label="r"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">r</figure-callout>}}^6+{\alpha }_4{r}^8$$
  
  in which :
  • c corresponds to the curvature of the surface of the optical element,
  • r at the radial distance to the optical axis,
  • k at the conical constant, and
  • α _{i [1, .., 4]} to the aspherical coefficients.
• the conical constant is less than -1, preferably less than -50;
• the conical constant is between -50 and -200;
• the curvature of said at least one surface of the optical element is between $\frac{1}{15}$
  
  mm ^-1 and $\frac{1}{5}$
  
  mm ^-1 ;
• the optical element has an opposite inner surface and an outer surface, such that the inner surface and the outer surface are of different general aspherical shapes;
• the inner surface and the outer surface satisfy equation (a);
• the conical constant is different between the equations (a) of the arrow of the inner surface and the outer surface of the optical element;
• the aspherical coefficients are different between the equations (a) of the arrow of the inner surface and the outer surface of the optical element;
• the optical element is configured to be arranged at a distance less than 5mm from the optics of the optical sensor, preferably less than 3mm from the optics of the optical sensor;
• the optical element is configured to be disposed upstream of the optics of the optical sensor so that the optical axis of the optical element coincides with the optical axis of the optical sensor;
• the optical element is rotatably mounted about an axis of rotation;
• the optical element is disposed centrally with respect to its axis of rotation;
• the optical element is arranged upstream of the protection device so as to face a road scene whose optical sensor is configured to take part in the shooting;
• said device comprises a housing secured to the optical element and having a housing configured to receive the optical sensor;
• the inner surface has an anti-fogging property, in particular the inner surface of said optical element has an anti-fog coating;
• the inner surface and / or the outer surface has at least one property chosen from the following list: infra-red, photocatalytic, hydrophobic, super hydrophobic, lipophobic, hydrophilic, super-hydrophilic, gravel-resistant.

The invention also relates to a driving assistance system comprising an optical sensor comprising an optical element. According to the invention, said system comprises a device for protecting the optical sensor as defined above.

According to one aspect of the invention, the optical element is distinct from the optical sensor.

• la figure 1 représente de façon schématique un véhicule automobile comprenant un système d'assistance à la conduite selon l'invention,
• la figure 2 est une vue en perspective d'un dispositif de protection d'un capteur optique du système d'assistance de la figure 1,
• la figure 3 est une vue en coupe longitudinale partielle du dispositif de protection de la figure 2,
• la figure 4 est une vue représentant de manière partielle et schématique un capteur optique du système d'assistance à la conduite et un élément optique de protection du capteur optique,
• la figure 5 représente de façon schématique une surface de forme générale asphérique de l'élément optique,
• la figure 6 est une variante du dispositif de protection, et
• la figure 7 est une autre variante du dispositif de protection.

Other features and advantages of the invention will appear more clearly on reading the following description, given by way of illustrative and non-limiting example, and the appended drawings among which:

• the figure 1 schematically represents a motor vehicle comprising a driving assistance system according to the invention,
• the figure 2 is a perspective view of a device for protecting an optical sensor of the assistance system of the figure 1 ,
• the figure 3 is a partial longitudinal sectional view of the protective device of the figure 2 ,
• the figure 4 is a view partially and schematically showing an optical sensor of the driver assistance system and an optical element for protecting the optical sensor,
• the figure 5 schematically represents a surface of generally aspherical shape of the optical element,
• the figure 6 is a variant of the protective device, and
• the figure 7 is another variant of the protection device.

In these figures, the identical elements bear the same references.

The following achievements are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply to a single embodiment. Simple features of different embodiments may also be combined or interchanged to provide other embodiments.

In the description, it is possible to index certain elements, such as for example first element or second element. In this case, it is a simple indexing to differentiate and name close but not identical elements. This indexing does not imply a priority of one element with respect to another and it is easy to interchange such denominations without departing from the scope of the present description. This indexing does not imply an order in time either.

The figure 1 shows a motor vehicle 100 equipped with at least one driving assistance system 1 according to the invention.

The driving assistance system 1 comprises in particular at least one optical sensor 13 and a protection device 3 of the optical sensor 13 represented on the figures 2 and 3 .

The optical sensor 13 (see Figures 1 to 3 ) is for example an optical sensor 13 for shooting such as a camera. It may be a CCD ("coupled coupled device") or a CMOS sensor comprising a matrix of miniature photodiodes. According to another variant, it may be a sensor for remote sensing laser called LIDAR sensor, acronym in English of "light detection and ranging".

As is best seen on the figures 2 and 3 the optical sensor 13 has an optic 14 optical axis 15. The optics 14 is for example an objective. An objective may comprise at least one lens, in particular several lenses depending on the field of vision and the resolution, for example between two and ten lenses, generally four or five lenses, even ten lenses in the case of a so-called fish-eye optics ("fish-eye" in English). At least one of the lenses of the optics 14 is for example convex (convex) convexity facing outwardly of the optical sensor 13, such as a so-called fish-eye optics ("fish-eye" in English).

The optical sensor 13 may further comprise a support portion 17 ( figure 3 ) of the optical sensor 13. This is a rear portion of the optical sensor 13 on the side opposite the optic 14.

According to the illustrated embodiment, the optical sensor 13 is intended to be mounted in the protection device 3. More precisely, the optical sensor 13 and in particular its support 17 are intended to be fixedly mounted in the protection device 3.

According to the example shown on the figure 1 , the protective device 3 is mounted at the front of the vehicle 100 at a bumper. Of course, alternatively the protection device 3 can be mounted at the rear of the vehicle 100, for example at the bumper or the license plate. It can also for example be mounted on the sides of the vehicle, for example at the mirrors.

The protective device 3 can be fixed according to any known technique, on any element 2 of the vehicle 100, such as a bodywork element or an external element such as a bumper, a rearview mirror or a license plate. For this purpose, there may be mentioned in a non-exhaustive manner a clip system, a screwing system, or a bonding system.

Protection device

• au moins un accessoire 4 pour véhicule automobile 100 (en se référant également à la figure 1), cet accessoire 4 étant monté mobile en rotation autour d'un axe de rotation A1 et ayant pour fonction la protection du capteur optique 13, et
• un actionneur, plus précisément un moteur 5, configuré pour entrainer en rotation l'accessoire 4.

More specifically, referring again to the figures 2 and 3 the protection device 3 comprises:

• at least one accessory 4 for a motor vehicle 100 (also referring to the figure 1 ), this accessory 4 being rotatably mounted about an axis of rotation A1 and having the function of protecting the optical sensor 13, and
• an actuator, more precisely a motor 5, configured to rotate the accessory 4.

The protective device 3 is therefore a motorized device.

In particular, the protection device 3 may comprise a first subassembly B and a second subset C which are distinct and assembled to one another. The first subassembly B may form the accessory 4 for a motor vehicle 100. The second subassembly C may comprise the engine 5, to drive in rotation the first subset B.

Accessory

The accessory 4 or means of protection may be at least partially transparent.

According to the embodiment described, the accessory 4 comprises an optical element 9. According to this embodiment, the accessory 4, and more generally the protection device 3 also advantageously comprises a housing 6 secured to the optical element 9.

The optical element 9 can be made in one piece with the housing 6. Alternatively, the housing 6 and the optical element 9 can be made by two separate parts secured.

The optical element 9 and the housing 6 are described in more detail below.

The optical element 9, better visible on the Figures 2 to 4 , is intended to protect the optics 14 of the optical sensor 13 possible projections of dirt or solid debris that could damage this optic 14. It is therefore a protective element, or more precisely a protective mask of the optical sensor 13, and it is this optical element 9 which is subjected to external aggression, that is to say both projections of water, pollutants, gravel pollutants or deposits of pollutants. traces of water.

According to the embodiment described, the optical element 9 is distinct from the optical sensor 13.

This optical element 9 has an optical axis 91.

The optical element 9 is arranged upstream of the protection device 3. In this example, the optical element 9 is arranged at the front of the protection device 3. In other words, the optical element 9 is arranged at the front of the accessory 4, or at the front of the housing 6. The front of the protection device 3 is the part intended to cope with to the road scene whose optical sensor 13 participates in the shooting, when the protection device 3 is mounted on the vehicle 100 ( figure 1 ). In contrast, the back of the protection device 3 is the opposite side to the front; it is therefore the furthest part of the road scene whose optical sensor 13 participates in the shooting.

More precisely, the optical element 9 is intended to be disposed upstream of the optical sensor 13, more precisely upstream of the optic 14. In the present, the term "upstream" is defined with respect to the optical axis 15 and relative to to the road scene whose optical sensor 13 participates in the shooting. In other words, it is understood by "upstream" of the optic 14, a position in which the optical element 9 is disposed between the optics 14 and the road scene whose optical sensor 13 participates in the shooting, according to the optical axis 15.

This optical element 9 is advantageously sized so as to cover the entire surface of the optic 14.

Arranged in the field of view of the optical sensor 13, the optical element 9 is advantageously transparent so as not to impair the efficiency of the optical sensor 13. This optical element 9 may be made of glass or a transparent plastic material such as polycarbonate.

The optical element 9 can be arranged centrally with respect to the optical sensor 13, more precisely centrally with respect to the optic 14. The optical element 9 is arranged so that its optical axis 91 coincides with the optical axis 15 of the optical sensor 13 (see figure 4 ).

In addition, the optical element 9 has at least one surface 9a, 9b of generally aspheric shape. More specifically, the portion of the optical element 9 intended to be arranged directly facing the optic 14 has this or these surfaces 9a, 9b of generally aspheric shape.

The surface 9a, respectively 9b, aspheric optical element 9 does not marry the shape of a sphere. In other words, the curvature of such an aspherical surface 9a, 9b is not constant at all points, unlike that of a sphere. The optical element 9 therefore does not have a simple spherical shape but is of more complex shape.

It should be noted that the optical element here is of aspherical shape, that is to say with a shape that is close to a spherical shape, and that this aspherical shape must be considered for a given thickness of the element. optical defined between a profile defining the inner surface of the optical element and a profile defining the outer surface of this optical element. It is the general profiles of the external and / or internal surfaces that must be taken into consideration and the presence of bead and / or spikes on the outer surface, in particular of the optical element, must not be taken into account here for the definition. of the aspherical form of the optical element.

The arrow z of each aspherical surface 9a, 9b, as a function of the radial distance r to the optical axis 91 of the optical element 9, is given by the following equation (a): $$z=\frac{{\mathit{<figure-callout\; id="2"\; label="cr"\; filenames="imgf0001.png"\; state="\{\{state\}\}">cr</figure-callout>}}^2}{1+\sqrt{1-\left(1+k\right){\mathrm{vs}}^2{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="imgf0001.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}}+{\alpha }_1{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="imgf0001.png"\; state="\{\{state\}\}">r</figure-callout>}}^2+{\alpha }_2{\mathrm{<figure-callout\; id="4"\; label="r"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">r</figure-callout>}}^4+{\alpha }_3{\mathrm{<figure-callout\; id="6"\; label="r"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">r</figure-callout>}}^6+{\alpha }_4{r}^8$$

mm^-1 et $\frac{1}{5}$

mm^-1.In this equation (a), the parameter c corresponds to the curvature of the surface of the optical element 9. This parameter c is the inverse of the radius of curvature R (see figure 5 ). The radius of curvature R varies with the distance to the optical axis 91. At a particular point, the radius of curvature R can be defined as that of the circle tangent to the surface at the point considered. Such a circle is called an osculating circle. Such a circle is represented schematically by a line with dashes on the figure 5 . According to a particular embodiment, the radius of curvature R is between 5mm and 15mm. The curvature c is therefore between $\frac{1}{15}$

mm ^-1 and $\frac{1}{5}$

mm ^-1 .

Moreover, in equation (a), the parameter r corresponds to the radial distance to the optical axis 91, as shown schematically in FIG. figure 4 .

The parameter k , not shown in the figures, corresponds to the conical constant, also called taper constant. It is a mathematical value representative of the variation of the curvature of the surface between its central part and its edges. In other words, the parameter k characterizes the variation of the radius of curvature R as one moves away from the vertex. This variation confers particular optical properties on the surfaces that possess this property of asphelity.

Finally, the parameters α _{i [1, .., 4]} correspond to the aspheric coefficients. In the equation (a) given above, the polynomial terms α ₁ r ² to α ₄ r ⁸ go up to a power 8 of the radial distance r , but of course there may be less of these polynomial terms or on the contrary, more.

These aspherical coefficients α _i are very small, especially less than 1. By way of non-limiting example, α ₁ is between 0.01 and 0.1; α ₂ between -10 ^-5 and -10 ^-6 ; α ₃ between 10 ^-9 and 10 ^-10 and α ₄ between 10 ^-10 and 10 ^-11 .

In a particular example, the aspheric surface forms a conical section.

In this case, the aspherical coefficients α _i are zero. The arrow z of the optical element 9 as a function of the radial distance r to the optical axis 91 of the optical element 9 is then given by the following equation (b): $$z=\frac{{\mathit{<figure-callout\; id="2"\; label="cr"\; filenames="imgf0001.png"\; state="\{\{state\}\}">cr</figure-callout>}}^2}{1+\sqrt{1-\left(1+k\right){\mathrm{vs}}^2{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="imgf0001.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}}$$

In this equation (b), the parameters c, k, r are the same as in equation (a). In other words, equation (b) corresponds to equation (a) with coefficients α _i zero.

Depending on the value of the conical constant k , the aspherical surface 9a, 9b can have different conical shapes, such as elliptical, parabolic or even hyperbolic.

According to a preferred embodiment, at least one surface 9a, 9b of the optical element 9 is of generally hyperbolic form. The arrow z of the surface 9a, 9b of general hyperbola form is given by equation (b). Moreover, in this equation (b), the conical constant k is less than -1, in particular much smaller than -1. Preferably, the conical constant k is less than -50, in particular the conical constant k is between -50 and -200.

Furthermore, the optical element 9 has an inner surface 9a and an outer surface 9a opposite. The inner surface 9a and the outer surface 9b each have a general aspherical shape, and in particular a general shape of hyperbola. The aspherical, or more precisely hyperbolic, shapes are different between the inner surface 9a and the outer surface 9b of the optical element 9. As previously, it is the general profile of the inner surface and the outer surface that must be taken in consideration for evaluating the aspherical shape, and in particular the shape of hyperbola, without taking into account the roughness of this surface and the presence of beads or pins modeling the surface state.

In particular, the conical constant k is different for the inner surface 9a and the outer surface 9b. According to a particular nonlimiting exemplary embodiment, the conical constant k of the order of -159 for one of the surfaces and -76 for the other surface.

In addition, the aspherical coefficients α _i are different in the equation (a) of the arrow z of the inner surface 9a and in that of the arrow z of the outer surface 9b.

Of course, as an alternative, the inner 9a and outer 9b surfaces may be parallel, that is to say that for these two surfaces 9a and 9b, one can have the same conical constant k and the same coefficients α _i in the equation (a) of the arrow z .

Furthermore, the surface 9a, respectively 9b, aspherical of the optical element 9 may be convex or concave. In this example, the optical element 9 is of generally convex shape. According to the illustrated example, it is the portion of the optical element 9 intended to be arranged in the field of view of the optical sensor 13, which has this substantially convex shape. Thus, the aspherical surfaces 9a, 9b of the optical element 9 are convex with their outwardly oriented convexities of the protection device 3.

In addition, the optical element 9 can be arranged at a distance d from the optic 14 (see figure 4 ) which is less than 5mm, or less than 3mm of the optic 14, for example of the order of 2mm. The optical element 9 can therefore be arranged very close to the optics 14 while maintaining a large viewing angle, especially greater than 110 °, for example of the order of 190 °, and good optical performance due to the surfaces. 9a, 9b aspherical. This makes the protection device 3 very compact. Indeed, the aspherical surfaces 9a, 9b offer a better optical performance with respect to an optical element that would be made with constant spherical surfaces. The overall hyperbolic shape of the inner 9a and outer 9b surfaces of the optical element 9 is particularly advantageous for such a small distance d between the optic 14 and the optical element 9.

Finally, the optical element 9 may have a very small thickness, for example of the order of a millimeter.

Furthermore, the optical element 9 is mounted to rotate about an axis of rotation A1, schematized on the figures 2 and 3 .

Advantageously, the axis of rotation A1 of the optical element 9 coincides with the optical axis 15 of the optical sensor 13. This axis of rotation A1 is also coincident with the optical axis 91 of the optical element 9.

The optical element 9 may be arranged centrally with respect to the axis of rotation A1. This optical element 9 has in particular a symmetry of revolution with respect to the axis of rotation A1.

Moreover, when the protection device 3 receiving the optical sensor 13 is mounted on the vehicle 100 (also referring to the figure 1 ), optics 14 and the element 9 advantageously protrude from an opening provided on the element 2 of the vehicle 100. With such an arrangement, the optical sensor 13 has a large viewing angle and the optic 14 remains clean due to the presence of the element 9 between the optics 14 and the outside of the vehicle 100 ( figure 1 ).

In addition, in order to avoid a phenomenon of condensation between the optic 14 and the optical element 9, the inner surface 9a of the optical element 9 (see FIG. figures 3-5 ) advantageously has an anti-fogging property. The inner surface 9a of the optical element 9 is the surface intended to be arranged opposite the optics 14 of the optical sensor 13. In particular the inner surface 9a of the optical element 9 has an anti-fog coating.

Alternatively or in addition, the inner surface 9a and / or outer 9b of the optical element 9 may have one or more of the following properties: hydrophobic, infra-red filter, photocatalytic, super hydrophobic, lipophobic, hydrophilic, or super hydrophilic , chipping resistance, or any other surface treatment to reduce the adhesion of dirt. In particular, thanks to the hydrophobic properties of the outer surface of the optical element 9, any drops of water will run on the outer surface without leaving any traces because the water will not adhere to this external surface. Thus, the layers or coatings on the outer surface 9b the optical element 9, limit the possibilities of adhesion of organic or inorganic pollutants and the presence of traces of water on the optical element 9 may be detrimental to the proper functioning Advantageously, a liquid solution, such as a Rain-X® solution, may be deposited on the outer surface 9b of the optical element 9 to form a hydrophobic film.

These exemplary embodiments are provided for illustrative and not limiting. For example, a person skilled in the art can use a transparent optical element 9 having an external surface 9b having other properties making it possible to limit the adhesion of dirt to this external surface 9b without departing from the scope of the present invention.

Optionally, the optical element 9 of the protection device 3 may also comprise an integrated defrosting or defogging system in order to guarantee good operability of the driver assistance system 1 whatever the weather conditions, such as a filament or a defrosting resistor for example.

Referring again to figures 2 and 3 , as regards the housing 6, it is rotatably mounted about the axis of rotation A1.

Preferably, the housing 6 is a waterproof housing. The housing 6 may be made of any suitable material known to those skilled in the art.

More specifically, this housing 6 is arranged to be rotated by the motor 5, which allows the rotation of the optical element 9. The optical element 9 is in this particular example, configured to be rotated with the housing 6, so as to allow cleaning of the optical element 9 by centrifugal effect.

The optical element 9 is configured to be disposed at the front of the housing 6. The front of the housing 6 is the part of the housing 6 intended to face the road scene whose optical sensor 13 participates in the when the protective device 3 is mounted on the vehicle 100 (also referring to the figure 1 ). In contrast, the rear of the housing 6 is the portion of the housing 6 opposite the front of the housing 6 and is the furthest part of the road scene whose optical sensor 13 participates in the shooting .

In addition, the optical sensor 13 is in this example mounted at least partly in the housing 6. To do this, the housing 6 comprises a housing 19 (see figure 3 ) configured to receive the optical sensor 13, for example so that the optical axis 15 of the optical sensor 13, coincides with the axis of rotation A1 of the housing 6.

More specifically, the housing 6 comprises a wall 21 defining the housing 19 for the optical sensor 13. This wall 21 may be centered around the axis of rotation A1 of the optical element 9 and the housing 6. In this example, the wall 21 is of generally cylindrical general shape.

According to a first variant, the wall 21 can be made in one piece with the optical element 9. According to a second variant, the wall 21 and the optical element 9 can be made by two separate parts, and in this case the wall 21 is secured at one end to the optical element 9. This is in particular the front end of the wall 21 which is secured to the optical element 9. By way of non-limiting example, the connection between the wall 21 and the optical element 9 can be done by ultrasonic welding. Thus, the housing 6 and the optical element 9 can be made in one or more rooms. The housing 6 being secured to the optical element 9, this forms a block sealing thus preventing the introduction of dirt inside the housing 6 for receiving the optical sensor 13.

Alternatively or additionally, advantageously at least one means for limiting condensation, hereinafter referred to as anti-condensation means. Such anti-condensation means can be provided at the housing 6. In particular, at least one anti-condensation means can be arranged on the wall 21 of the housing 6.

By way of non-limiting example, the anti-condensation means may comprise at least one orifice 210 passing through the housing 6, in this example on the wall 21 (see FIG. figure 3 ). The orifices 210 may be made by drilling. Preferably, when several orifices 210 are provided, they are arranged symmetrically with respect to the axis of rotation A1 of the housing 6.

According to the example shown on the figure 3 , two orifices 210 are provided, arranged symmetrically with respect to the axis of rotation A1 of the housing 6. The orifices 210 communicate between the inside of the housing 6 and the outside of the housing 6 when the protection device 3 is assembled . By way of non-limiting example, each orifice 210 may have a diameter of the order of 5 mm.

In addition, one or more semi-permeable membranes 211 may be provided, respectively arranged at least at an orifice 210. According to the example illustrated in FIG. figure 3 two membranes 211 are shown schematically. Each membrane 211 may be attached to a port 210 associated sealingly, for example by gluing or by ultrasonic welding. These membranes 211 are, according to the described embodiments, permeable to air and impermeable to water. The membrane or membranes 211 thus promote the flow of air inside the housing 6. This allows good ventilation between the optical 14 and the optical element 9 and thus prevents the accumulation of condensation.

Advantageously, provision is furthermore made for at least one means for compensating the mass removed at the orifice 210 or the orifices 210. According to the particular example illustrated in FIG. figure 3 , the two membranes 211 are placed symmetrically with respect to the axis of rotation A1 of the housing 6 and it is this symmetrical arrangement which makes it possible to limit the effects of mass with respect to the centrifugal force during the rotation of the housing 6 .

Engine

With regard to the engine 5, different variants of which are represented on the figures 2 , 3 , 6 and 7 it may be in particular a small electric motor or even miniature.

By small electric motor is meant in the context of the present invention a stepper motor, an actuator, a DC motor with or without a brush, an asynchronous motor or a synchronous motor, whose mass is less than 10 kg, even less than 1kg, in particular used to operate equipment for vehicles.

By miniature electric motor is meant in the context of the present invention a stepper motor, an actuator, a DC motor with or without brushes, an asynchronous motor or a synchronous motor, whose mass is less than 200g or less at 100 g, preferably between 30 g and 100 g, for example between 30 g and 60 g.

The motor 5 comprises a rotor 51 and a fixed stator 53, the rotor 51 being able to rotate with respect to the fixed stator 53.

The motor 5 is coupled to the housing 6 to rotate the housing 6 and the optical element 9. According to the embodiment described, the housing 6 and the optical element 9 are integral with the rotor 51 of the motor 5.

According to the embodiment illustrated on the figures 2 , 3 and 6 , the rotor 51 is disposed around the stator 53. The stator 53 is therefore inside and the rotor 51 outside. Moreover, in the example of figure 6 , the stator 53 can form the support 17 of the optical sensor 13. In other words, the support 17 and the stator 53 are made in one piece.

Alternatively, as illustrated on the figure 7 the stator 53 can be arranged around the rotor 51.

Moreover, according to the different embodiments illustrated on the figures 2 , 3 , 6 and 7 , the motor 5 is arranged at the rear of the protection device 3, more precisely the motor 5 is assembled at the rear of the housing 6. In other words, the motor 5 is arranged on the opposite side to the optical element 9.

A sealed block is thus formed, thus preventing the introduction of dirt inside the housing 6 intended to receive the optical sensor 13.

In addition, the motor 5 is in this example arranged in the extension of the optical sensor 13.

The motor 5 is advantageously a hollow motor. He can receive at least part the optical sensor 13.

According to the configuration illustrated on the figure 3 with the internal stator 53 and the external rotor 51, the stator 53 can receive at least part of the support 17 of the optical sensor 13.

According to the configuration illustrated on the figure 6 with the outer rotor 51 and the stator 53 forming the optical medium 17, the hollow rotor 51 can receive at least part of the stator 53 forming a support 17 of the optical sensor 13.

According to the configuration illustrated on the figure 7 , with the internal rotor 51, it is the latter which can receive at least part of the support 17 of the optical sensor 13.

The motor 5 is for example electrically powered by a power supply connected to the general electrical circuit of the vehicle 100 (also referring to the figure 1 ).

As a non-limiting example, the motor 5 may be more particularly a brushless motor, also known under the name "brushless motor" in English. According to the example shown on the figure 3 the motor 5 comprises at least one magnet 55 integral with the rotor 51, and a predefined number of electromagnetic coils 57, in particular at least three electromagnetic coils 57 mounted on the stator 53. The electromagnetic coils 57 are intended to be powered to enable the electromagnetic coils 57 to drive of the magnet 55 secured to the rotor 51. The motor 5 comprises for this purpose a control circuit 59 for the supply of the electromagnetic coils 57. This control circuit 59 can be connected to a connected power supply harness 61 to the general electrical circuit of the vehicle 100 (also referring to figure 1 ).

The motor 5 can have a rotation speed of between 1000 and 50000 revolutions / minute, preferably between 5000 and 20000 revolutions / minute, and more preferably between 7000 and 15000 revolutions / minute. Such rotational speeds allow the removal of any soil that would have deposited on the optical element 9 by centrifugal effect and thus maintain the optics 14 of the optical sensor 13 clean to ensure optimized operation of the assistance system to driving 1.

The motor 5 is configured to rotate the accessory 4, namely in this example the housing 6 and the optical element 9 integral with the housing 6.

The motor 5 is rotatably mounted about an axis of rotation A2. The motor 5 is for example arranged so that its axis of rotation A2 coincides with the axis of rotation A1 of the optical element 9, and with the optical axis 15 of the optical sensor 13.

Furthermore, it is advantageous to provide a sealed arrangement at the rear of the motor 5 for the passage of cables or wires in order to limit the entry of water vapor and / or other contaminants into the protective device 3.

The protective device 3 thus comprises a movable part 31, also called a rotating part 31, and a fixed part 33 (see figure 3 ).

The movable part 31 comprises at least the rotor 51 of the motor 5, and the fixed part 33 comprises at least the stator 53 of the motor 5.

The movable portion 31 of the motorized device 3 may also comprise at least one movable element integral with the rotor 51, such as in particular the accessory 4, that is to say the housing 6 and the optical element 9 in this example.

Similarly, the fixed portion 33 may also comprise an element or support fixed to the stator 53. Of course, the element or support may be fixed directly or not to the stator 53. Without limitation, in this example, the fixed part 33 the motorized device 3 comprises the fixed support 17 of the optical sensor 13. This fixed support 17 is in particular fixed to the stator 53.

The support 17 of the optical sensor 13 and the stator 53 advantageously have respective complementary openings 63, 65 to enable the control circuit 59 to be connected to the power supply harness 61.

In addition, the protection device 3 may comprise in particular one or more bearings 27, 28 represented schematically on the figure 3 . According to this example, the protection device 3 comprises two bearings 27, 28.

These bearings 27, 28 are each arranged between the movable portion 31 and the fixed portion 33 of the protection device 3. The bearings 27, 28 are generally substantially annular. In addition, the two bearings 27, 28 are arranged concentrically with the motor 5.

Referring to the particular example illustrated on the figure 3 , one of the bearings, for example the bearing 27 may be disposed between the rotor 51 and a portion, in particular a front portion, of the support 17 of the optical sensor 13. The other bearing, the bearing 28 in the example of the figure 3 , is disposed between the rotor 51 and the stator 53 of the motor 5.

Alternatively, the two bearings 27 and 28 can be arranged between the rotor 51 and the stator 53. In particular, according to the embodiment variant illustrated on the figure 5 , the two bearings 27, 28 are arranged between the rotor 51 and the stator 53 forming a support 17 of the optical sensor 13.

Moreover, at least one of these bearings 27, 28 may be a magnetic bearing. Such a magnetic bearing avoids the noise and friction generally caused during operation of the protective device 3 using mechanical bearings.

According to one variant, a bearing may be magnetic and the other bearing may be a mechanical bearing such as a ball bearing. According to another variant, the motorized device 3 may comprise a single magnetic bearing.

Thus, by arranging only a few millimeters of the optic 14 of the optical sensor 13, an optical element 9 with surfaces 9a, 9b having such a complex, aspherical or even hyperbolic shape, a compact protection device 3 is obtained, protecting against external soiling. optics 14 of the optical sensor 13 while ensuring a relatively large field of view, for example of the order of 190 °.

In addition, the rotation of this optical element 9, in particular via the housing 6, ensures that the field of view of the optical sensor 13 is always clear and clean. The rotation of the optical element 9 ensures the removal of dirt due to the centrifugal force that they undergo.

Claims (10)

Protective device (3) for an optical sensor (13) for a motor vehicle (100), said optical sensor (13) comprising an optical element (14), characterized in that the protection device (3) comprises an optical element ( 9) configured to be disposed upstream of the optics (14) of the optical sensor (13) and having at least one surface (9a, 9b) of generally aspherical shape. Device (3) according to the preceding claim, wherein said at least one surface (9a, 9b) is a hyperbolic surface. Device (3) according to claim 1 or 2, wherein the arrow (z) of said at least one surface (9a, 9b) of the optical element (9) as a function of the radial distance ( r ) to the axis optical (91) of the optical element (9) is given by equation (a): $$z=\frac{{\mathit{cr}}^2}{1+\sqrt{1-\left(1+k\right){\mathrm{vs}}^2{r}^2}}+{\alpha }_1{r}^2+{\alpha }_2{r}^4+{\alpha }_3{r}^6+{\alpha }_4{r}^8$$

in which : c corresponds to the curvature of the surface of the optical element (9), r at the radial distance to the optical axis (91), k at the conical constant, and - α _{i [1, .., 4]} to the aspherical coefficients. Device (3) according to the preceding claim, wherein the conical constant (k) is less than -1, preferably less than -50, in particular the conical constant (k) is between -50 and -200. Device (3) according to claim 3 or 4, wherein the curvature (c) of said at least one surface (9a, 9b) of the optical element (9) is between $\frac{1}{15}$

mm ^-1 and $\frac{1}{5}$

mm ^-1 . Device (3) according to any one of the preceding claims, wherein the optical element (9) has an opposite inner surface (9a) and outer surface (9b), such as the inner surface (9a) and the outer surface (9b) are of different general aspherical shapes. Device (3) according to claims 3 and 6, wherein the inner surface (9a) and the outer surface (9b) satisfies the equation (a) and the aspherical coefficients ( α _i ) are different between the equations (a) of the arrow (z) of the inner surface (9a) and the outer surface (9b) of the optical element (9). Device (3) according to any one of the preceding claims, wherein the optical element (9) is configured to be arranged at a distance ( d ) of less than 5mm from the optics (14) of the optical sensor (13), preferably less than 3mm from the optics (14) of the optical sensor (13). Device (3) according to any one of the preceding claims, wherein the optical element (9) is rotatably mounted about an axis of rotation (A1). Driver assistance system (1) comprising an optical sensor (13) comprising an optic (14), characterized in that said system (1) further comprises a protection device (3) of the optical sensor (13) according to any one of the preceding claims.

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